<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>class定义CSS</title>
  <style>
    .box1 {
      color: red;
      font-size: 20px;
      background: lightblue;
      margin: 5px;
      padding: 5px;
      width: 300px;
      height: 100px;
      line-height: 100px;
      text-align: center;
    }
    .myinput {
      height: 50px;
      width: 88%;
      background-color: aqua;
    }
  </style>
</head>
<body>
<div>1111</div>
<div class="box1">2222</div>
<div class="box1">3333</div>
<div>
  <input class="myinput" type="email" name="email" value="ming206@qq.com">
</div>
</body>
</html>